When it comes to e-mail, there’s no such thing as a one-size-fits-all solution. I’ve learned that lesson emphatically over the last year as I’ve tested a variety of different e-mail solutions for myself and for various friends and clients.

The top-secret Technology Reviewers Handbook says that after all that evaluating I’m supposed to pick a winner. But there is no clear winner. Instead, I’m happily using three different e-mail systems:

My business e-mail i running on a hosted Exchange account at Intermedia. My wife’s business account is hosted on the same server. (I’ve written previously about my reasons for choosing Exchange 2010; I switched to Intermedia earlier this year because they offered Exchange 2010 when other hosted Exchange providers were still offering Exchange 2007.)

I have a single user account at Office 365 for several upcoming projects, where features other than e-mail were the deciding factor.

I’m playing Google Apps administrator for an out-of-state client who needed a free, easy e-mail solution that would work well with his new Android phone.

Why three different solutions? Because each client (including myself) had different needs. I sorted them out by asking a series of questions and thought it might be useful to share my decision tree here.

A note: If you live in the United States, your options should be the same as the ones I write about in this post. In other countries, some services might not be available, and others might be offered at different prices. In addition, I do not cover the many educational offerings available for students and others associated with an educational institution.

1. Do you want a store-and-forward server or one that syncs your messages in the cloud?

Most Internet service providers offer POP3 mailboxes. They’re usually a standard feature with cheap web-hosting plans, too. These accounts use store-and-forward servers that assume you’re downloading your messages to a local store and deleting them off the server immediately. The server isn't designed to keep an archive. Your master copy of any message is local.

By contrast, cloud-based mail products store your messages on a server so that you can access your e-mail—all of it, new and old—via a web browser. You can usually sync the server’s message store with a local PC or device, using Exchange ActiveSync or IMAP.

For this question, I think there's only one correct answer. If you work in a big corporation, a central server that stores every user's messages is a key part of a legally acceptable archiving policy. But a cloud-based server is also a good idea even if you’re a one-person organization. If you have more than one device (smartphone and PC, maybe a notebook, maybe a tablet), keeping everything in sync with a POP3 account is impossible. I still have a few POP3 accounts associated with some domains I own, but I forward all incoming messages from those accounts to a cloud-based account.

2. Do you need a custom domain?

I’m a firm believer in owning your own domain—especially for business mail. You might be perfectly happy to use a generic webmail address as your calling card to the rest of the world. (Just don't adopt an address from your ISP as your primary e-mail account. If you move or change service providers, that address will become useless.)

The free Google Apps offering allows you to assign your custom domain to Google Apps. Hotmail offers this feature, too, but the domain management tools in Windows Live Admin Center made me want to scream in frustration. For my out-of-state clients, it took a few hours to get their custom domain working with Google Apps, but after those initial hiccups were out of the way it’s been problem-free.

Naturally, all of the paid services—hosted Exchange, Office 365, and Google Apps—offer excellent integration with custom domains. For Office 365 and Intermedia, I had a choice of turning an entire domain over or just defining mail exchange (MX) records. If you know your way around DNS configuration, this is a straightforward task. If you don’t, be prepared to ask for help (or take a crash course in DNS management).

Here's the DNS manager for an Office 365 P plan. Note that you must set up the MX records with an external DNS service and can't edit them here:

And here's the custom DNS manager that Intermedia customers find in the HostPilot control panel:

3. Do you plan to use Microsoft Outlook?

If you live in Outlook, then your primary account should be on an Exchange 2010 server. Period. Full stop.

The combination of Outlook and Exchange offers great online and offline support. That’s true whether you’re using Microsoft’s Office 365 or a hosted Exchange option like Intermedia’s. Hotmail accounts work well after you install the Microsoft Outlook Hotmail Connector.

My experience with accessing Gmail and Google Apps accounts via Microsoft Outlook has been consistently bad—so bad that I won’t use the two products together. I won’t recommend that combination for anyone else, either. If you have a Gmail account and you want offline access, you can use the Offline settingsin Google's Chrome browser or try a third-party client program other than Outlook.

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4. Are you willing to pay? If so, how much?

If you want free, get Hotmail or Gmail. (And don’t turn up your nose at Hotmail. If you haven’t looked lately, I recommend you try it again. It’s a first-class webmail solution that would have armies of fans if it came out of Mountain View or Cupertino.)

Google Apps is also available as a free offering. It’s limited to 10 user accounts, and each account has the same server storage as a free Gmail account—currently just over 7 GB.

Prices start at roughly $50 a year, and you can get a lot of extra services along with your e-mail package. The most important, as far as I’m concerned, is the dedicated support that isn’t available with the free services (more about that later). Google offers a variety of add-ons for its Google Apps for Business customers. Microsoft includes SharePoint and Lync Online (messaging and collaboration) with Office 365. Those latter add-ons were the reason I chose Office 365 for my next book.

Google Apps: the free version allows up to 10 user accounts, with the same email storage limits as a free Gmail account. Google Apps for Business bumps storage to 25 GB and adds BlackBerry and Microsoft Outlook interoperability costs; it costs $5 per user account per month, or $50 if paid annually.

Intermedia Hosted Exchange: $7.50 per mailbox per month for Business account (25 GB storage), or $10/month for Enterprise account with unlimited storage and a 50 MB SharePoint plan; additional SharePoint storage is available for a fee.

5. How good is the spam filtering?

This is the question most people forget to ask. In my case, there was an enormous difference. Gmail, Hotmail, and Office 365 were equally effective at separating the wheat from the chaff, with a low incidence of real messages swept into the Junk folder.

[Update; A reader points out that with Office 365 E plans, administrators have access to Forefront for Exchange.]

Intermedia offers much more fine-grained control. Every message that goes through its SpamStopper engine is assigned a numeric score. The higher the score, the more likely a particular message is likely to be spam. Using the sliders in the SpamStopper section of HostPilot allows you to set thresholds based on those scores, with messages above a certain score being moved to the Junk folder or summarily deleted.

One of my e-mail addresses has been in use since 1994. It gets mountains of spam every day—I estimate more than 90% of the messages sent to that address are spam. Unfortunately, I can’t retire the address, so I simply forward it to another account at a different domain. It is a real-world stress test for any spam filter.

With Office 365, I would typically get hundreds of messages from this address shunted into my Junk folder every day. Trying to pick the occasional legitimate message out was unpleasant work, and I know I missed a few important messages. By contrast, the Intermedia filters allowed me to filter spam using the numeric rating attached to each message after it was analyzed. I was able to quickly tweak those settings so that only a handful of actual spam messages sneak through every day. That makes the false positives much easier to spot and whitelist.

6. Do you need human support?

When it comes to support, you definitely get what you pay for.

With free Gmail, Hotmail, and Google Apps accounts, and with the $6-per-month Office 365 Plan P, you get only online support (typically via user-to-user forums). Google Apps for Business and the E-for-Enterprise Office 365 plans offer more robust support options.

But they can’t hold a candle to Intermedia’s support, which it legitimately touts as “industry leading.” I used their free migration service with a test account last fall to copy the contents of my Gmail account to corresponding folders in the new Exchange store. Since I moved my primary business and personal accounts to Intermedia, I’ve needed to call for support on several occasions. Hold times were brief, and the engineers I talked to were able to address my issues quickly and accurately.

They were especially good at helping me track down external causes for issues, including DNS configurations, that were affecting e-mail delivery. When I was briefly experiencing some routing issues on Comcast’s network, Intermedia’s engineers contacted Comcast to fix the issue. That was a refreshing change from the usual finger-pointing that goes on.

In my case, the combination of excellent spam filtering and great support were enough to tip the scales heavily in Intermedia’s favor. Ironically, Intermedia recently announced that it plans to resell Office 365 services. You can bet I'll be monitoring that development closely.

And that’s my list.

If you’ve gone through a similar decision process, it’s possible your calculations were different. Tell me about it in the Talkback section.